Sea Foam to clear injector buggers

D

DSigmond

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C Dory Year
2007
C Dory Model
22 Cruiser
Hull Identification Number
WN7747NU
I have a 10 year old Yamaha 115, 4 stroke, with something like 300 hours. It starts promptly, but has lost power and WOT RPMs max out at about 4 grand. To my knowledge it has only had ethanol-free fuel, sometimes with Yami oil addition, and Stable over winter.

I've heard good stuff for Sea Foam cleaning injectors, car-heads lean to Lucas Injector Cleaner in the gas.

So any experience & thoughts. How much to use, and when to give up for a mechanic shop a month down the road...
 
Yes I use Sea Foam in a lot of equipment both gas and diesel and I feel it does help, particularly with use in about every 3rd tank. With 300 hours if the motor has never been serviced if is way past time particularly if years of age and hour are since last service to include plugs, fluids and filters.
I don't like running fuel in my boat motors older than a few months anytime and I pump out fuel if older than a year and run thru other gas burning things that operate on land. Fuel filters then plugs and again oil and filter would be a good start for me if I had your current issues and had kept up with maintenance intervals
 
Yamaha suggests use of Yamaha "Ring Free plus". I would use an injector cleaner rather than the Sea Foam.

Is there any growth on the bottom of the boat? Prop damage, excessive weight in the boat?
 
This sounds like the problem I had with my 2006 115 Yamaha. Wouldn't go over about 4000 rpm, but would start fine and run good at lower rpms.
Turned out to be a slightly clogged filter at the intake of the high pressure fuel pump. Unfortunately, in order to get at the little dime-sized filter, the intake manifold has to be removed to gain access to the VST (vapor separation tank) where the HP fuel pump lives. The filter is on the bottom of the pump, and it was only partially blocked, but enough to cause the issue.
Chris
 
I had the very same issue that you described on my 225 HP Yamaha. It was the exact same issue that Chris outlined. The water had set in the bottom long enough, that the part had to be replaced, due to pitting. It was not a cheap fix, but was the only thing that could be done, to make it run correctly.
 
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